On complex power nonnegative matrices

Power nonnegative matrices are defined as complex matrices having at least one nonnegative integer power. We exploit the possibility of deriving a Perron Frobenius-like theory for these matrices, obtaining three main results and drawing several consequences. We study, in particular, the relationships with the set of matrices having eventually nonnegative powers, the inverse of M-type matrices and the set of matrices whose columns (rows) sum up to one

Keep focussing: striatal dopamine multiple functions resolved in a single mechanism tested in a simulated humanoid robot

The effects of striatal dopamine (DA) on behavior have been widely investigated over the past decades, with "phasic" burst firings considered as the key expression of a reward prediction error responsible for reinforcement learning. Less well studied is "tonic" DA, where putative functions include the idea that it is a regulator of vigor, incentive salience, disposition to exert an effort and a modulator of approach strategies. We present a model combining tonic and phasic DA to show how different outflows triggered by either intrinsically or extrinsically motivating stimuli dynamically affect the basal ganglia by impacting on a selection process this system performs on its cortical input. The model, which has been tested on the simulated humanoid robot iCub interacting with a mechatronic board, shows the putative functions ascribed to DA emerging from the combination of a standard computational mechanism coupled to a differential sensitivity to the presence of DA across the striatum

Could cadmium be responsible for some of the neurological signs and symptoms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

According to the World Health Organization, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a neurological disease characterized by widespread inflammation and multi-systemic neuropathology. Aetiology and pathogenesis are unknown, and several agents have been proposed as causative agents or as factors perpetuating the syndrome. Exposure to heavy metals, with particular reference to mercury and gold in dental amalgams, has been considered among the triggers of ME/CFS. Here we hypothesize that cadmium, a widespread occupational and environmental heavy metal pollutant, might be associated with some of the neurological findings described in ME/CFS. In fact, ME/CFS patients show a decrease of the volume of the gray matter in turn associated with objective reduction of physical activity. Cadmium induces neuronal death in cortical neurons through a combined mechanism of apoptosis and necrosis and it could then be hypothesized that cadmium-induced neuronal cell death is responsible for some of the effects of cadmium on the central nervous system, i.e. a decrease in attention level and memory in exposed humans as well as to a diminished ability for training and learning in rats, that are symptoms typical of ME/CFS. This hypothesis can be tested by measuring cadmium exposure in a cohort of ME/CFS patients compared with matched healthy controls, and by measuring gray matter volume in un-exposed healthy controls, exposed non-ME/CFS subjects, un-exposed ME/CFS patients and exposed ME/CFS patients. In addition, we hypothesize that cadmium exposure could be associated with reduced cerebral blood flow in ME/CFS patients because of the disruptive effects of cadmium on angiogenesis. In fact, cadmium inhibits angiogenesis and low global cerebral flow is associated with abnormal brain neuroimaging results and brain dysfunction in the form of reduced cognitive testing scores in ME/CFS patients. This hypothesis can be tested by measuring cerebral cortex blood flow in un-exposed healthy controls, exposed non-ME/CFS subjects, un-exposed ME/CFS patients and exposed ME/CFS patients. If our hypothesis is demonstrated correct, the consequences could affect prevention, early diagnosis, and treatment of ME/CFS. Implications in early diagnosis could entail the evaluation of symptoms typical of ME/CFS in cadmium-exposed subjects as well as the search for signs of exposure to cadmium in subjects diagnosed with ME/CFS. Nutritional supplementation of magnesium and zinc could then be considered, since these elements have been proposed in the prophylaxis and therapy of cadmium exposure, and magnesium was demonstrated effective on ME/CFS patients' symptom profiles

Mediterranean diet and metabolic status in post-menopausal women living in a mediterranean area

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A novel role for a major component of the vitamin D axis: vitamin D binding protein-derived macrophage activating factor induces human breast cancer cell apoptosis through stimulation of macrophages.

The role of vitamin D in maintaining health appears greater than originally thought, and the concept of the vitamin D axis underlines the complexity of the biological events controlled by biologically active vitamin D (1,25(OH)(2)D3), its two binding proteins that are the vitamin D receptor (VDR) and the vitamin D-binding protein-derived macrophage activating factor (GcMAF). In this study we demonstrate that GcMAF stimulates macrophages, which in turn attack human breast cancer cells, induce their apoptosis and eventually phagocytize them. These results are consistent with the observation that macrophages infiltrated implanted tumors in mice after GcMAF injections. In addition, we hypothesize that the last 23 hydrophobic amino acids of VDR, located at the inner part of the plasma membrane, interact with the first 23 hydrophobic amino acids of the GcMAF located at the external part of the plasma membrane. This al1ows 1,25(OH)(2)D3 and oleic acid to become sandwiched between the two vitamin D-binding proteins, thus postulating a novel molecular mode of interaction between GcMAF and VDR. Taken together, these results support and reinforce the hypothesis that GcMAF has multiple biological activities that could be responsible for its anti-cancer effects, possibly through molecular interaction with the VDR that in turn is responsible for a multitude of non-genomic as well as genomic effects

Series solution of beams with variable cross-section

Abstract In structural engineering beams with non-constant cross-section or beams with variable cross-section represent a class of slender bodies, aim of practitioners' interest due to the possibility of optimizing their geometry with respect to specific needs. Despite the advantages that engineers can obtain from their applications, non-trivial difficulties occurring in the non-prismatic beam modeling often lead to inaccurate predictions that vanish the gain of the optimization process. As a consequence, an effective non-prismatic beam modeling still represents a branch of the structural engineering of interest for the community, especially for advanced design applications in large spans elements. A straight beam of length l with variable inertia J(z) is provided in figure, subject to a generic live load condition q(z). The vertical displacement y(z) can be obtained from the solution of the differential equation of the elastic line, i.e., taking into consideration the inertia variability and neglecting, as first approximation, any shear contribution. Even if this solution is an approximate one, it is able to deal with the problem in its basic formulation. In this paper a solution for the problem stated is formulated using a series expansion of solutions, in a general load and cross section variability condition. Solution is thus obtained for a generic rectangular cross section beam with a variable height. Analytical solution is presented and evaluated using numerical evaluation of some cases of practical interest

X-ray irradiated cultures of mouse cortical neural stem/progenitor cells recover cell viability and proliferation with dose-dependent kinetics

Exposure of the developing or adult brain to ionizing radiation (IR) can cause cognitive impairment and/ or brain cancer, by targeting neural stem/progenitor cells (NSPCs). IR effects on NSPCs include transient cell cycle arrest, permanent cell cycle exit/differentiation, or cell death, depending on the experimental conditions. In vivo studies suggest that brain age influences NSPC response to IR, but whether this is due to intrinsic NSPC changes or to niche environment modifications remains unclear. Here, we describe the dose-dependent, time-dependent effects of X-ray IR in NSPC cultures derived from the mouse foetal cerebral cortex. We show that, although cortical NSPCs are resistant to low/moderate IR doses, high level IR exposure causes cell death, accumulation of DNA double-strand breaks, activation of p53- related molecular pathways and cell cycle alterations. Irradiated NSPC cultures transiently upregulate differentiation markers, but recover control levels of proliferation, viability and gene expression in the second week post-irradiation. These results are consistent with previously described in vivo effects of IR in the developing mouse cortex, and distinct from those observed in adult NSPC niches or in vitro adult NSPC cultures, suggesting that intrinsic differences in NSPCs of different origins might determine, at least in part, their response to IR